Small folder is definitely better for climbing. Go serrated if he's not going to keep it sharp, PE if he's a knife knut (but it sounds like not).
Some things to look at: Spyderco Dragonfly, Native, Delica, Atlantic Salt, Pacific Salt. Partially serrated might be the best - serrated portion for cutting rope, plain edge for whittling tinder for a fire. Benchmade Griptillian. If you want to go a little higher end, I recommend the Spyderco Ocelot - nice G10, strong point. Could also consider a Paramilitary.
I'm betting if you go smaller and lighter, he'll be more likely to take it along and use it - which is why the Dragonfly tops the list. No sense getting something he's not going to use. A tiny little Dragonfly or Ladybug in his pack will do infinitely more good than the Ranger at home.
I carried a Gerber LST and Leatherman Micra as my hiking kit for a long time, supplemented with a pocket wire saw. Never had trouble cutting up dinner or starting a fire, though cooking was done on a stove. Lately, I've taken to carrying a Benchmade AFCK, or a small fixed blade (Pukko, Busse Mean Street, Reeve Mountaineer IV, etc.) mostly because I have them and might as well them. The Reeve is awesome at cutting cheese, the Busse is pretty awful. The fixed blades are overkill for climbing - at best they'd be really expensive, A2 pitons.
It's tough buying knives for people. Good luck.